A display device using a non-self-luminous display panel such as, for example, a liquid crystal display panel is used typically in combination with a lighting device that illuminates the display panel from behind. A lighting device of this type uses any of various types of light sources including a cold cathode tube, a light emitting element, and the like. Examples of a light emitting element include a light emitting diode (hereinafter, referred to as an “LED”), an organic electroluminescent element, an inorganic electroluminescent element, and the like, among which the most commonly used today is an LED. A lighting device described in Patent Document 1 also uses an LED as a light source.
In the lighting device described in Patent Document 1, as shown in FIG. 8, LEDs 122 are mounted on a mounting substrate 121, and a lens 124 that covers each of the LEDs 122 is mounted to the mounting substrate 121. The mounting substrate 121, each of the LEDs 122, and the lens 124 constitute a light emitting module mj. A multitude of the light emitting modules mj are disposed in a matrix form to form a planar light source.
While in the lighting device described in Patent Document 1, a multitude of point light sources are arranged, in a lighting device described in Patent Document 2, a multitude of linear light sources such as cold cathode tubes are arranged. In a case where a display device is used in combination with a lighting device in which a plurality of light sources are arranged in this manner, light from the light sources directly entering the lighting device leads to unevenness in brightness on a screen, and hence, in order to prevent this, a diffusion plate that diffuses light is disposed between the light sources and the display device. As is also the case with Patent Document 2, a diffusion plate is generally used as a constituent component of a lighting device.
The light sources in a state of being mounted on a mounting substrate are assembled to a chassis of the lighting device. A mounting substrate, from which not much can be expected in terms of light reflection, is typically covered with a reflection sheet so that only light sources are exposed therefrom. An example of such a lighting device including a reflection sheet can be found in Patent Document 3.
Even in a case where a diffusion plate and a reflection sheet are used, the luminance on the diffusion plate is decreased at an outer peripheral portion thereof compared with that at a center portion thereof. In Patent Document 4, such a decrease in luminance at an outer peripheral portion is compensated for by disposing LEDs that are linearly mounted on an inner wall of a chassis.